Soya bean (Glycine maxL.) evapotranspiration under unlimited and water stress conditions as affected by weather

Soya bean's growing area has increased in Hungary since the 2000s, yet few direct field-based evapotranspiration measurements are available. Compensation evapotranspirometer was used to control two watering levels (unlimited and water stress limited to flowering) at Hungary (45 degrees N), in a three-season study (2017-2019). Two soya bean varieties with different water demands,SinaraandSigalia,were analysed. During these vegetation periods, the total evapotranspiration in unlimited water level (both varieties) was above 600 mm, while water stress during flowering reduced it to about half. Water losses in the wet 2018 were slightly lower than during the dry 2017 and 2019. Correlation coefficient values between evapotranspiration and weather variables implied that water losses were controlled by available energy and relative humidity in dry and wet seasons, respectively. Using easily accessible meteorological variables, the air temperature was found to be the best estimator of evapotranspiration. Due to water stress under flowering, the seasonal mean yields varied irregularly in both varieties. Irrespective to season, the water productivity for grain showed a trend to lower values in unlimited watering compared to water stress conditions. Crop-water response in both soya bean varieties would offer valuable information for breeders and seed distributors in identifying better varieties under mild continental climate.